ServletContext.getRealPath(".") returns null on Windows

Usually servletContext.getRealPath(".") is used to determine the servlet context root directory of the application.
When using the FileResourceManager in a DeploymentInfo this call returns null because of the "file.getCanonicalFile().getName().equals(file.getName())" check.
When using servletContext.getRealPath ("") it works as expected, but that leads to problems in other AppServers.